1. Field of the Invention
This invention relates to ultrasonic surgical instruments useful in removing tissue from within a biological structure, and more particularly to such an instrument having curved transmitting and/or amplifying structure to enable clear vision of the operating site with minimum loss of energy.
2. Description of the Prior Art
Surgical instruments utilizing ultrasonic vibrations in combination with the circulation of irrigation liquid over the operative site for the removal of tissue in a biological body are well known and widely used particularly in enclosed or substantially enclosed operative sites such as encountered in the removal of cataracts, brain tumors and other organ neoplasms. The known ultrasonic surgical aspirators of this type, generally referred to herein as ultrasonic aspirators, conventionally employ an elongated probe having one end rigidly attached through a vibration transmission member to a transducer for supplying ultrasonic energy, and having its other end portion adapted to be inserted into the operative site where the transmitted ultrasonic energy is emitted from the tip. Tissue particles are dislodged and broken up or emulsified by the ultrasonic energy and removed by the aspiration of irrigation fluid from the site.
The known ultrasonic handpieces generally employ piezoelectric elctromechanical transducers capable of transforming high frequency electrical energy into correspondingly high frequency mechanical impulses which are transmitted through the probe to the operative tip in a standing wave pattern. Such transducers require an enclosure or housing to provide the electrical connections required, to support the vibrating structure, to contain any circulating fluid necessary to cool the transducer, and to provide a surface that is not also vibrating for holding and manipulating the assembly. The housing, generally referred to as a handpiece, is dimensioned to fit comfortably into the surgeon's hand for easy manipulation and control during the surgical procedure.
One known ultrasonic surgical aspirator is disclosed in U.S. Pat. No. 3,805,787 and includes conduits for applying suction through the center of the vibration transmitting probe and for supplying irrigation fluid around the outer surface of the probe through a passage defined by a sleeve or shield. Irrigation fluid flows around the free end of the tubular probe element and back through the center of the probe to effectively irrigate and remove dislodged and emulsified tissue. Shield arrangements for controlling or directing the flow of irrigation fluid in the vicinity of the probe tip may be provided in accordance with this pior art patent, and U.S. Pat. No. 3,693,613 discloses a flow control system for avoiding the application of excessive pressure or suction at the operative site by such ultrasonic aspirator.
The known ultrasonic aspirators have employed straight ultrasonic transmission probes extending coaxially with the handpiece. Since the handpiece is substantially larger in diameter than the probe, and further since the handpiece is held in the surgeon's hand during use, view of the operative site at the tip of the probe is frequently obscured and consequently such devices are of limited use in removing tissue deep within a biological structure where the surrounding anatomy cannot be retracted or the opening made large enough to allow good visibility. Two examples of such situations are the extraction of brain tumors involving the optic nerve and removal of tumors within the colon. The application of the prior art straight ultrasonic aspirators is also particularly limited in microsurgery because the handpiece and the surgeon's hand often physically interfere with the surgical operating microscope, making simultaneous use of these instruments awkward if not impossible. Thus, however advantageous the application of intense ultrasonic vibration in the presence of irrigation and aspiration may be to surgery, the use of straight structures to provide this function limits the type and location of the malady amenable to approach.
Methods of and apparatus for transmitting longitudinal ultrasonic vibrations through both straight and curved structures, and for amplifying the intensity of the vibrations while undergoing such transmission are known. For example, U.S. Pat. No. 3,546,498 discloses a curved sonic transmission line in which the transmission element is made up of a series of straight and curved segments, the curves being relatively short radius bends located at critical locations, i.e., at the anodes in the vibrating transmission element. However, curved transmission elements have not been used in surgical ultrasonic aspirators despite the advantages to be obtained because, it is believed, that it has not been considered possible for longitudinal waves containing sufficient energy to be propagated through a curved transmission element independently of flexural waves of excessive magnitude and without such flexural waves interfering with the desired longitudinal movement of the operative tip of the probe.